Deepening a spark plug
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Deepening a spark plug
When I install a regular long sized spark plug in my cylinder head, it is 2-3 threads bellow the surface of the combustion chamber, I could swap the crush washer for a copper hydraulic washer probably but it wont leave me any room for indexing the plugs.
Is there a way I can deepen the spark plug hole without going to a machine shop? it's an aluminum head.
Is there a way I can deepen the spark plug hole without going to a machine shop? it's an aluminum head.
Re: Deepening a spark plug
Is it the head manufacturer recommended plug?ELS wrote: ↑Tue Jun 14, 2022 5:06 am When I install a regular long sized spark plug in my cylinder head, it is 2-3 threads bellow the surface of the combustion chamber, I could swap the crush washer for a copper hydraulic washer probably but it wont leave me any room for indexing the plugs.
Is there a way I can deepen the spark plug hole without going to a machine shop? it's an aluminum head.
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
Re: Deepening a spark plug
what does that matter for? I said it was the long style plug, I've never seen a longer plug than those regular long plugs, and the recommended plug isn't made anymore and is even a bit shorter still.HQM383 wrote: ↑Tue Jun 14, 2022 5:35 amIs it the head manufacturer recommended plug?ELS wrote: ↑Tue Jun 14, 2022 5:06 am When I install a regular long sized spark plug in my cylinder head, it is 2-3 threads bellow the surface of the combustion chamber, I could swap the crush washer for a copper hydraulic washer probably but it wont leave me any room for indexing the plugs.
Is there a way I can deepen the spark plug hole without going to a machine shop? it's an aluminum head.
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Re: Deepening a spark plug
Can you post up a picture of what's taking place?
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Deepening a spark plug
torqued down, no indexing washers ofc.
I don't want to grind out the combustion chamber because I'm already struggling to get descent CR as it is, though maybe it'd be possible to deepen the spark plug mounting surface.
oh and the spark plugs are angled to the same side on all the cylinders, meaning that on cylinders 1 and 3 they are angled towards the exhaust and have a good chance of having the spark inside the combustion chamber, but on cylinders 2 and 4 they are angled towards the intake but have the intake side obstructed
in the picture cylinder #3 is shown
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Re: Deepening a spark plug
I'll perhaps try to weld and harden some screw drivers (because that's the highest carbon content steel I have around) into a cutter, then hollow out an old plug and install it from the combustion chamber as a guide.
hopefully the coolant jacket isn't closer to the threads deeper in the plug hole
hopefully the coolant jacket isn't closer to the threads deeper in the plug hole
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Re: Deepening a spark plug
Most plugs are .750" in length. Bosch makes a plug (suffix H0) that is .840". Or, many extended tip plugs might work evenELS wrote: ↑Tue Jun 14, 2022 5:55 amwhat does that matter for? I said it was the long style plug, I've never seen a longer plug than those regular long plugs, and the recommended plug isn't made anymore and is even a bit shorter still.HQM383 wrote: ↑Tue Jun 14, 2022 5:35 amIs it the head manufacturer recommended plug?ELS wrote: ↑Tue Jun 14, 2022 5:06 am When I install a regular long sized spark plug in my cylinder head, it is 2-3 threads bellow the surface of the combustion chamber, I could swap the crush washer for a copper hydraulic washer probably but it wont leave me any room for indexing the plugs.
Is there a way I can deepen the spark plug hole without going to a machine shop? it's an aluminum head.
with standard length.
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Re: Deepening a spark plug
I'll look into them, but I'd prefer using the regular 3/4' size, since all my favorite plugs are in thatDavid Redszus wrote: ↑Tue Jun 14, 2022 10:24 amMost plugs are .750" in length. Bosch makes a plug (suffix H0) that is .840". Or, many extended tip plugs might work even
with standard length.
about the cutter thing I said I was gonna do, well it turned out successful, until it broke... didn't bother to reduce it's hardness and it bit me in the ass
made it from a gutted out plug for the guide, an 8mm rod from a screwdriver, a 3/16" file iirc for the cutter bit.
tried drilling trough the cutter, but couldn't even when I annealed it, it was too hard for my crappy 1.5mm drill.
it sunk the plug down maybe like .7mm,
although I used it on the 2nd cylinder instead of the 3rd which I compared it to... precision analysis!
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Re: Deepening a spark plug
There are some plugs that have a longer projected tip than what was considered normal. Check with NGK to see if available in your thread size.
Re: Deepening a spark plug
well I specifically want to deepen the spark plug bore instead of using more uncommon plugs, but I think I have that figured out, just have to make a new cutter and I'll probably solder the cutter blade in the shaft so it doesnt move this time. or weld it but I dont have a lot of space for that
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Re: Deepening a spark plug
Just note that if you go to a extended tip plug that you may want to start off one heat range cooler until you see what there color change over point looks like after a few long full throttle runs.
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Deepening a spark plug
well I made another cutter, this time using a 14mm steel bar and turning it down to 8mm at the end for the guide.
fit is terrible because the drill I used to 'lathe it' had the chuck slightly crooked, but I centered the blade as close as I could before soldering it so it's fine.
after 15 minutes of cutting I didn't even get the spark plug 180 degrees deepened (this time I used it on the #3 cylinder for a proper comparison).
I wanted to use a drill but I'll have to rig up some 'loose' connection between the cutter and drill, so the cutter doesnt get moved laterally by the drill.
oh and btw if you're interested, the spark plug thread size is M14x1.25
fit is terrible because the drill I used to 'lathe it' had the chuck slightly crooked, but I centered the blade as close as I could before soldering it so it's fine.
after 15 minutes of cutting I didn't even get the spark plug 180 degrees deepened (this time I used it on the #3 cylinder for a proper comparison).
I wanted to use a drill but I'll have to rig up some 'loose' connection between the cutter and drill, so the cutter doesnt get moved laterally by the drill.
oh and btw if you're interested, the spark plug thread size is M14x1.25
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Re: Deepening a spark plug
update: using a drill, that cutter cuts like butter. too fast even, 1 second too much and it cuts a milimeter too deep.
and the soldered blade holds up fine, so no welding needed
photo of the finished cutter and guide
and the soldered blade holds up fine, so no welding needed
photo of the finished cutter and guide
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